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    SubjectRe: CONFIG_PREEMPT and server workloads
    On Fri, Mar 19, 2004 at 11:30:16AM +0100, Takashi Iwai wrote:
    > > The unavoidable worst case is in the RCU callbacks for dcache shrinkage -
    > > I've seen 25 millisecond holdoffs on the above machine during filesystem
    > > stresstests when RCU is freeing a huge number of dentries in softirq
    > > context.
    >
    > hmm, this wasn't also evaluated in my tests.
    > it's worthy to try. thanks for the info.

    Please do. This would be a very interesting data point.

    >
    > > This if Hard To Fix. Dipankar spent quite some time looking into it and
    > > had patches, but I lost track of where they're at.
    >
    > couldn't this tasklet be replaced with workqueue or such?

    Close. I am using per-cpu kernel threads to hand over the rcu callbacks
    if there are too many of them. It depends on CONFIG_PREEMPT on better
    latency from there onwards.

    I can use a workqueue, but I needed the flexibility experiment with
    the kernel thread for now.

    Thanks
    Dipankar
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